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breakpilot-lehrer/klausur-service/backend/cv_syllable_detect.py
Benjamin Admin a8773d5b00 Fix 4 Grid Editor bugs: syllable modes, heading detection, word gaps
1. Syllable "Original" (auto) mode: only normalize cells that already
   have | from OCR — don't add new syllable marks via pyphen to words
   without printed dividers on the original scan.

2. Syllable "Aus" (none) mode: strip residual | chars from OCR text
   so cells display clean (e.g. "Zel|le" → "Zelle").

3. Heading detection: add text length guard in single-cell heuristic —
   words > 4 alpha chars starting lowercase (like "zentral") are regular
   vocabulary, not section headings.

4. Word-gap merge: new merge_word_gaps_in_zones() step with relaxed
   threshold (6 chars) fixes OCR splits like "zerknit tert" → "zerknittert".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-27 15:24:35 +01:00

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"""
Syllable divider insertion for dictionary pages.
For confirmed dictionary pages (is_dictionary=True), processes all content
column cells:
1. Strips existing | dividers for clean normalization
2. Merges pipe-gap spaces (where OCR split a word at a divider position)
3. Applies pyphen syllabification to each word >= 3 alpha chars (DE then EN)
4. Only modifies words that pyphen recognizes — garbled OCR stays as-is
No CV gate needed — the dictionary detection confidence is sufficient.
pyphen uses Hunspell/TeX hyphenation dictionaries and is very reliable.
Lizenz: Apache 2.0 (kommerziell nutzbar)
DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
"""
import logging
import re
from typing import Any, Dict, List, Optional, Tuple
import numpy as np
logger = logging.getLogger(__name__)
# IPA/phonetic characters — skip cells containing these
_IPA_RE = re.compile(r'[\[\]ˈˌːʃʒθðŋɑɒæɔəɛɜɪʊʌ]')
# Common German words that should NOT be merged with adjacent tokens.
# These are function words that appear as standalone words between
# headwords/definitions on dictionary pages.
_STOP_WORDS = frozenset([
# Articles
'der', 'die', 'das', 'dem', 'den', 'des',
'ein', 'eine', 'einem', 'einen', 'einer',
# Pronouns
'er', 'es', 'sie', 'wir', 'ihr', 'ich', 'man', 'sich',
# Prepositions
'mit', 'von', 'zu', 'für', 'auf', 'in', 'an', 'um', 'am', 'im',
'aus', 'bei', 'nach', 'vor', 'bis', 'durch', 'über', 'unter',
'zwischen', 'ohne', 'gegen',
# Conjunctions
'und', 'oder', 'als', 'wie', 'wenn', 'dass', 'weil', 'aber',
# Adverbs
'auch', 'noch', 'nur', 'schon', 'sehr', 'nicht',
# Verbs
'ist', 'hat', 'wird', 'kann', 'soll', 'muss', 'darf',
'sein', 'haben',
# Other
'kein', 'keine', 'keinem', 'keinen', 'keiner',
])
# Cached hyphenators
_hyph_de = None
_hyph_en = None
def _get_hyphenators():
"""Lazy-load pyphen hyphenators (cached across calls)."""
global _hyph_de, _hyph_en
if _hyph_de is not None:
return _hyph_de, _hyph_en
try:
import pyphen
except ImportError:
return None, None
_hyph_de = pyphen.Pyphen(lang='de_DE')
_hyph_en = pyphen.Pyphen(lang='en_US')
return _hyph_de, _hyph_en
def _hyphenate_word(word: str, hyph_de, hyph_en) -> Optional[str]:
"""Try to hyphenate a word using DE then EN dictionary.
Returns word with | separators, or None if not recognized.
"""
hyph = hyph_de.inserted(word, hyphen='|')
if '|' in hyph:
return hyph
hyph = hyph_en.inserted(word, hyphen='|')
if '|' in hyph:
return hyph
return None
def _try_merge_pipe_gaps(text: str, hyph_de) -> str:
"""Merge fragments separated by single spaces where OCR split at a pipe.
Example: "Kaf fee" -> "Kaffee" (pyphen recognizes the merged word).
Multi-step: "Ka bel jau" -> "Kabel jau" -> "Kabeljau".
Guards against false merges:
- The FIRST token must be pure alpha (word start — no attached punctuation)
- The second token may have trailing punctuation (comma, period) which
stays attached to the merged word: "" + "fer," -> "Käfer,"
- Common German function words (der, die, das, ...) are never merged
- At least one fragment must be very short (<=3 alpha chars)
"""
parts = text.split(' ')
if len(parts) < 2:
return text
result = [parts[0]]
i = 1
while i < len(parts):
prev = result[-1]
curr = parts[i]
# Extract alpha-only core for lookup
prev_alpha = re.sub(r'[^a-zA-ZäöüÄÖÜßẞ]', '', prev)
curr_alpha = re.sub(r'[^a-zA-ZäöüÄÖÜßẞ]', '', curr)
# Guard 1: first token must be pure alpha (word-start fragment)
# second token may have trailing punctuation
# Guard 2: neither alpha core can be a common German function word
# Guard 3: the shorter fragment must be <= 3 chars (pipe-gap signal)
# Guard 4: combined length must be >= 4
should_try = (
prev == prev_alpha # first token: pure alpha (word start)
and prev_alpha and curr_alpha
and prev_alpha.lower() not in _STOP_WORDS
and curr_alpha.lower() not in _STOP_WORDS
and min(len(prev_alpha), len(curr_alpha)) <= 3
and len(prev_alpha) + len(curr_alpha) >= 4
)
if should_try:
merged_alpha = prev_alpha + curr_alpha
hyph = hyph_de.inserted(merged_alpha, hyphen='-')
if '-' in hyph:
# pyphen recognizes merged word — collapse the space
result[-1] = prev + curr
i += 1
continue
result.append(curr)
i += 1
return ' '.join(result)
def merge_word_gaps_in_zones(zones_data: List[Dict], session_id: str) -> int:
"""Merge OCR word-gap fragments in cell texts using pyphen validation.
OCR often splits words at syllable boundaries into separate word_boxes,
producing text like "zerknit tert" instead of "zerknittert". This
function tries to merge adjacent fragments in every content cell.
More permissive than ``_try_merge_pipe_gaps`` (threshold 6 instead of 3)
but still guarded by pyphen dictionary lookup and stop-word exclusion.
Returns the number of cells modified.
"""
hyph_de, _ = _get_hyphenators()
if hyph_de is None:
return 0
modified = 0
for z in zones_data:
for cell in z.get("cells", []):
ct = cell.get("col_type", "")
if not ct.startswith("column_"):
continue
text = cell.get("text", "")
if not text or " " not in text:
continue
# Skip IPA cells
text_no_brackets = re.sub(r'\[[^\]]*\]', '', text)
if _IPA_RE.search(text_no_brackets):
continue
new_text = _try_merge_word_gaps(text, hyph_de)
if new_text != text:
cell["text"] = new_text
modified += 1
if modified:
logger.info(
"build-grid session %s: merged word gaps in %d cells",
session_id, modified,
)
return modified
def _try_merge_word_gaps(text: str, hyph_de) -> str:
"""Merge OCR word fragments with relaxed threshold (max_short=6).
Similar to ``_try_merge_pipe_gaps`` but allows longer fragments to be
merged. Still requires pyphen to recognize the merged word.
"""
parts = text.split(' ')
if len(parts) < 2:
return text
result = [parts[0]]
i = 1
while i < len(parts):
prev = result[-1]
curr = parts[i]
prev_alpha = re.sub(r'[^a-zA-ZäöüÄÖÜßẞ]', '', prev)
curr_alpha = re.sub(r'[^a-zA-ZäöüÄÖÜßẞ]', '', curr)
should_try = (
prev == prev_alpha
and prev_alpha and curr_alpha
and prev_alpha.lower() not in _STOP_WORDS
and curr_alpha.lower() not in _STOP_WORDS
and min(len(prev_alpha), len(curr_alpha)) <= 6
and len(prev_alpha) + len(curr_alpha) >= 4
)
if should_try:
merged_alpha = prev_alpha + curr_alpha
hyph = hyph_de.inserted(merged_alpha, hyphen='-')
if '-' in hyph:
result[-1] = prev + curr
i += 1
continue
result.append(curr)
i += 1
return ' '.join(result)
def _syllabify_text(text: str, hyph_de, hyph_en) -> str:
"""Syllabify all significant words in a text string.
1. Strip existing | dividers
2. Merge pipe-gap spaces where possible
3. Apply pyphen to each word >= 3 alphabetic chars
4. Words pyphen doesn't recognize stay as-is (no bad guesses)
"""
if not text:
return text
# Skip cells that contain IPA transcription characters outside brackets.
# Bracket content like [bɪltʃøn] is programmatically inserted and should
# not block syllabification of the surrounding text.
text_no_brackets = re.sub(r'\[[^\]]*\]', '', text)
if _IPA_RE.search(text_no_brackets):
return text
# Phase 1: strip existing pipe dividers for clean normalization
clean = text.replace('|', '')
# Phase 2: merge pipe-gap spaces (OCR fragments from pipe splitting)
clean = _try_merge_pipe_gaps(clean, hyph_de)
# Phase 3: tokenize and syllabify each word
# Split on whitespace and comma/semicolon sequences, keeping separators
tokens = re.split(r'(\s+|[,;:]+\s*)', clean)
result = []
for tok in tokens:
if not tok or re.match(r'^[\s,;:]+$', tok):
result.append(tok)
continue
# Strip trailing/leading punctuation for pyphen lookup
m = re.match(r'^([^a-zA-ZäöüÄÖÜßẞ]*)(.*?)([^a-zA-ZäöüÄÖÜßẞ]*)$', tok)
if not m:
result.append(tok)
continue
lead, word, trail = m.group(1), m.group(2), m.group(3)
if len(word) < 3 or not re.search(r'[a-zA-ZäöüÄÖÜß]', word):
result.append(tok)
continue
hyph = _hyphenate_word(word, hyph_de, hyph_en)
if hyph:
result.append(lead + hyph + trail)
else:
result.append(tok)
return ''.join(result)
def insert_syllable_dividers(
zones_data: List[Dict],
img_bgr: np.ndarray,
session_id: str,
*,
force: bool = False,
col_filter: Optional[set] = None,
) -> int:
"""Insert pipe syllable dividers into dictionary cells.
For dictionary pages: process all content column cells, strip existing
pipes, merge pipe-gap spaces, and re-syllabify using pyphen.
Pre-check: at least 1% of content cells must already contain ``|`` from
OCR. This guards against pages with zero pipe characters (the primary
guard — article_col_index — is checked at the call site).
Args:
force: If True, skip the pipe-ratio pre-check and syllabify all
content words regardless of whether the original has pipe dividers.
col_filter: If set, only process cells whose col_type is in this set.
None means process all content columns.
Returns the number of cells modified.
"""
hyph_de, hyph_en = _get_hyphenators()
if hyph_de is None:
logger.warning("pyphen not installed — skipping syllable insertion")
return 0
# Pre-check: count cells that already have | from OCR.
# Real dictionary pages with printed syllable dividers will have OCR-
# detected pipes in many cells. Pages without syllable dividers will
# have zero — skip those to avoid false syllabification.
if not force:
total_col_cells = 0
cells_with_pipes = 0
for z in zones_data:
for cell in z.get("cells", []):
if cell.get("col_type", "").startswith("column_"):
total_col_cells += 1
if "|" in cell.get("text", ""):
cells_with_pipes += 1
if total_col_cells > 0:
pipe_ratio = cells_with_pipes / total_col_cells
if pipe_ratio < 0.01:
logger.info(
"build-grid session %s: skipping syllable insertion — "
"only %.1f%% of cells have existing pipes (need >=1%%)",
session_id, pipe_ratio * 100,
)
return 0
insertions = 0
for z in zones_data:
for cell in z.get("cells", []):
ct = cell.get("col_type", "")
if not ct.startswith("column_"):
continue
if col_filter is not None and ct not in col_filter:
continue
text = cell.get("text", "")
if not text:
continue
# In auto mode (force=False), only normalize cells that already
# have | from OCR (i.e. printed syllable dividers on the original
# scan). Don't add new syllable marks to other words.
if not force and "|" not in text:
continue
new_text = _syllabify_text(text, hyph_de, hyph_en)
if new_text != text:
cell["text"] = new_text
insertions += 1
if insertions:
logger.info(
"build-grid session %s: syllable dividers inserted/normalized "
"in %d cells (pyphen)",
session_id, insertions,
)
return insertions